Preliminary evaluation of probiotic effects on gastrointestinal signs in dogs with multicentric lymphoma undergoing multi‐agent chemotherapy: A randomised, placebo‐controlled study

BACKGROUND: Gastrointestinal (GI) toxicity is a major dose‐limiting factor in dogs undergoing chemotherapy. A proposed mechanism of GI toxicity includes chemotherapy‐driven GI dysbiosis. This study was designed to determine the effects of probiotic administration on GI side‐effects in dogs receiving multi‐agent chemotherapy. METHODS: Ten client‐owned dogs with multicentric lymphoma were enrolled in a prospective, randomised, placebo‐controlled single‐blinded study. On the first day of the cyclophosphamide doxorubicin vincristine prednisone (CHOP)‐based chemotherapy protocol, dogs were randomised to receive either daily oral probiotic at a dose of 200 × 10(9) cfu/10 kg (n = 5) or daily oral placebo (n = 5). Complete blood count, faecal score (FS), faecal microbiome analysis (qPCR) and adverse events scores were performed at baseline and on the day of each subsequent chemotherapy dose, as well as 3 days after doxorubicin (days 0, 7, 14, 21, 24 and 28). RESULTS: Overall, 40% of dogs had an abnormal GI microbiome at baseline, specifically decreased faecal C. hiranonis and Fusobacterium abundances. Dogs receiving probiotics had increased faecal Streptococcus (p = 0.02) and E. coli. (p = 0.01). No dogs receiving probiotics experienced diarrhoea (FS ≥ 3.5) compared to four of five receiving placebo. (F 2.895; p = 0.13) CONCLUSION: GI microbiome dysbiosis was common in this group of dogs with multicentric lymphoma. Probiotics were well‐tolerated, with no negative side effects. Further studies are needed to explore broader microbiome and metabolome changes, as well as clinical benefit.